Repetitive energy transfers from an inductive energy store



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Texas Tech University


This dissertation details the theoretical and experimental results of a research program aimed at finding practical ways to transfer energy repetitively from an inductive energy store to various loads. The objectives were to investigate and develop the high power opening switches and transfer circuits needed to enable highrepetition-rate operation of such systems, including a feasibility demonstration at a current level near 10 kA and a pulse repetition rate of 1-10 kpps with a 1-ohm load. The requirements of nonlinear, time-varying loads, such as the railgun electromagnetic launcher, were also addressed. Energy storage capability is needed for proper power conditioning in systems where the duty factor of the output pulse train is low. Inductive energy storage is attractive because it has both a high energy storage density and a fast discharge capability. However, to transfer energy from a coil or inductor to a load, an opening switch must be used to interrupt the current and insert the load into the circuit. The switch must carry the large coil current during the storage time, interrupt the current, and then withstand the high voltage generated by the coil current flowing through the load. The opening switch problem is difficult enough for single-shot operation in many applications, but it becomes formidable when repetitive operation is required. By producing a pulse train with a peak power of 75 MW at a pulse repetition rate of 5 kpps in a one-ohm load system, this research program was the first to demonstrate fully-controlled, high-power, high-repetition-rate operation of an inductive energy storage and transfer system with survivable switches. Success was made possible by using triggered vacuum gap switches as repetitive, current-zero opening switches and developing several new repetitive transfer circuits using the counterpulse technique. A detailed analysis of the switching and transfer process was made and the dependency of the output pulse risetime on specific load conditions was determined. Finally, repetitive railgun operation was enabled (in theory) by developing new transfer circuits capable of recovering the energy remaining in the load inductance after each output pulse.